The invention relates to a supporting-arch construction, in particular for vaults of industrial furnaces, such as vertical lime kilns, as set forth below.
The invention also relates to a process for producing a supporting arch, as also set forth below.
Vault structures or supporting-arch structures are required in structural engineering, in particular in construction using shaped bodies or shaped blocks, wherever a region has a cavity beneath it and the load of the structure or masonrywork located above the cavity has to be diverted to the walls or pillars bounding the cavity laterally. Since the time of the Romans, in many sacred and also secular buildings, supporting arches or vaults have helped to span cavities with roofs or false floors or to produce bridges. The vaults or supporting arches here can achieve considerable spans and divert laterally into the masonrywork or auxiliary structures, such as columns and pillars, forces which are introduced at their apex or the arch surfaces.
It is also the case in industrial-furnace construction that use is made of vaults and supporting arches of different spans in order to provide a furnace cavity which can have further cavities or masonry structures constructed above it. It is generally customary for vaults or supporting-arch structures to be constructed such that first of all a center is produced, for example from wood, and then, from two sides to the apex, the blocks which form the supporting arch of the vault are built up thereon in opposite directions as far as the apex. A so-called keystone is then introduced at the apex and, with support against said keystone taking place on all sides in the case of domes and on two sides in the case of supporting arches or supporting barrel vaults, the supporting arch is supported against the keystone by way of its two oppositely directed sections. The center can then be removed and the vault or the supporting arch stands freely.
DE 39 33 744 C2 discloses a set of keystones for installation in the transition region between two oppositely directed sections of a vault-like supporting structure made of refractory blocks. In the case of this known structure for supporting arches, the supporting structure is formed from two sections which are directed toward one another in opposite directions, the set of keystones being inserted in the transition region between the two sections and comprising two transition stones which on their outside, adjacent to the respectively last block of the corresponding section, have a groove/tongue profile which tapers conically from top to bottom, is designed to correspond to the appropriate groove/tongue arrangements of the adjacent block and is thus intended to make it possible for the blocks to be laid securely in a close-fitting manner, and the set of keystones further comprising at least one keystone which is shaped such that it can be inserted axially in a form-fitting manner into the space between the previously inserted stones. This is intended to ensure that, in the case of repairs, this keystone has to be removed axially, as a result of which the supporting structure is opened in order for it to be possible for further stones or blocks to be removed and exchanged in the case of repair. Theoretically, this is intended to achieve the situation where, for the purpose of opening the supporting arch, the keystone, rather than being capable of being removed upward into the region of a masonry structure located thereabove, can be drawn out axially without part of the masonry structure located thereabove having to be removed. This known embodiment has not proven successful in practice and has therefore been modified to the effect that the grooves and tongues have steps (FIG. 14) which make possible a somewhat higher stability against lateral axial pressure. As a result, however, it is necessary for the keystone to be drawn out radially upward from the supporting arch, with the result that there is no longer any advantage achieved over conventional keystones for vault structures. A considerable disadvantage, however, is that the set of keystones comprises three stones and thus gives rise to considerably increased production outlay in comparison with normal keystones.
EP 0 862 034 B1 likewise discloses a set of keystones for a vault made of refractory blocks, comprising two adapter stones, which can be connected to the refractory blocks in a force-fitting manner, and a wedge-shaped keystone, it being possible for the wedge-shaped keystone to be inserted axially into the space between the adapter stones which is to be closed, and the adapter stones and the keystone being inserted into a joint bed of mortar. In the case of this known structure, the connection surfaces of the adapted stones and of the keystone which are supported against one another in the installed state are designed as planar, step-free surfaces, grooves being arranged in said surfaces and, following the insertion of the keystone, supplementing one another to form a channel which is axially open on the end sides, with the result that the channels each accommodate a solid coupling rod, which can be introduced at the end sides, made of a plain carbon steel. The disadvantage with this embodiment of a set of keystones or of a supporting arch is that, as a result of different materials being introduced, the supporting arch is inhomogeneous both in chemical terms and in terms of materials and, in particular, the coupling rods may burn out during use, with the result that permanent stability is not provided.
CH 453 568 discloses a similar solution, in this case the channels being formed and/or bounded by metal plates pushed in between the stones, this solution being envisaged for brick linings for rotary kilns.
DE-A 21 19 051 proposes, for the vault-like brick lining of rotary kilns, so-called voussoirs having obliquely running wedge-shaped protrusions in their side walls. In order to complete an arch or a circle of the rotary kiln, use is made of keystones which have one smooth side surface which is vertical or inclined in relation to the base surface, while the other side surface has the shoulder, or the necessary wedge-shaped protrusion, which is needed for connection to the rest of the blocks. It is also disadvantageous, in the case of such an embodiment, that axial forces cannot be reliably absorbed at least in the region of the keystone.
DE-C 481 676 discloses a block for furnace-chamber ceilings which, on one of its side surfaces, has a V-shaped protrusion with an upwardly directed tip and, on an opposite surface, has a corresponding groove. The protrusion and groove are each continued downward as far as a glazed bottom surface of the block, the protrusion and groove each being in the form of a closed triangle. This is intended to avoid the situation where ruptures along certain lines result in the broken-off parts dropping out, with corresponding exposure of non-glazed parts of the ceiling to the heat, and the ceiling is rapidly destroyed. According to this document, it is necessary, during the construction of an annular firing surface using these shaped bodies, for wedge-shaped stones to be inserted into suitable interspaces. These stones are designed in the same way as the abovementioned blocks, but have a smooth surface without any protrusion or a groove. It is also disadvantageous here that, in the region of the voussoir or of the voussoirs, the supporting arch is weakened, in particular in the axial direction. It is further disadvantageous that the keystone, for repair work, has to be drawn out of the supporting arch in the upward direction over the entire stone height.
It is an object of the invention to provide a supporting-arch construction which results in a straightforwardly constructed supporting arch and can be installed more easily and with less outlay, and has a higher load-bearing strength, than known supporting arches.
The object is achieved by a supporting-arch construction having the features set forth below.
Advantageous developments are specified below.
It is also an object to provide a process for producing a supporting arch by means of which a supporting arch can be installed reliably, easily and with little outlay and the supporting arch achieved is one with high load-bearing strength.
The object is achieved by a process for producing supporting arch having the features set forth below.
According to the invention, a supporting arch is formed by way of a standard block format, i.e. there are no separate adapters or keystones required.
It is only the imposts of the supporting arch which, as is also customary in the prior art, are of a different shape. On the supporting arch side, they correspond, as far as the surface is concerned, essentially to a supporting-arch-block format and, on a bearing-side surface, the latter surface is smooth. The block formats of the supporting-arch structure according to the invention have a specifically designed contour with a step which has a shape and a ramp angle which, surprisingly, has been found to be statically particularly stable.
The process according to the invention makes provision for the arch to be constructed from one abutment block, beyond the apex, and for the last block which is to be inserted to be the abutment voussoir or impost which rests on the other abutment block opposite. This has the advantage that, in the case of a repair, the masonry structure located above the supporting arch, in the vast majority of cases, need not be broken out at all since, at the location at which the impost is inserted, there is usually a gap, between this block and the masonry structure above, which is filled with mortar.
It is thus advantageous in the case of the invention that supporting arches can be produced straightforwardly and reliably, reduced production outlay rendering the supporting arches favorable, and the supporting arch according to the invention or the supporting-arch construction according to the invention being statically very highly loadable.